Based on the-federation.info, it looks like over the last ~3 days #Fediverse added about four BlueSky's worth of active users. 

That spike there is roughly 800k monthly active accounts.

Obviously measuring this is difficult, and there are weird bumps like the one about a month ago (visible on the chart), but this time it is confirmed by other metrics sources.

Not all of #NewHere will stay, just like in previous waves. But many will. And it will make fedi more diverse and fun. 🎉